1. Technical Field
This disclosure relates generally to integrated circuit layout, and more particularly to data correcting an integrated circuit layout incorporating a critical dimension (CD) correction.
2. Background Art
Double patterning has become a primary solution to continually decrease resolution as the limits of optical lithography are reached. However, several technical issues need to be addressed with double patterning. For the case of “photoresist on photoresist” double patterning, where the first pattern and the second pattern have intersecting areas, the second resist will be required to image over topography. This may also be true for cases of double patterning that require the resist to be imaged on a pattern that has been previously etched. For many common designs it is required that the second resist prints with a single critical dimension (CD) in both thin regions and thick regions, as the second resist traverses topography of the first photoresist image. However, it is known that the CD will shift with resist thickness due to the “bulk” and/or “swing” effects, as well as focus variations. As shown in FIG. 1, designed layout 2 includes second pattern 6 intersect first pattern 4 in portion 8. Due to the bulk effect, the CD 6(1) as printed in resist of the second pattern is biased as portion 8(1) is narrower than the designed layout portion 8. FIG. 1 is merely one example of this effect. Depending upon the thickness change of the resist, the size and shape of the structures, and tone (positive or negative) of each structure, it is possible to have a wide variety of CD image distortions as the second resist traverses the topography of the first resist.